1. Field of the Invention
The present invention relates to an optical disk drive, and more particularly, to reading of data from an out-of-specification CD such as a copy-controlled CD.
2. Related Art
In the field of a digital audio compact disk (CD-DA) that carries audio data and control data, there has been known a (copy protection) technique for reading data through use of an optical disk drive, such as a CD drive, provided in a personal computer (PC), and preventing copying of the data to another CD or the like. A CD having undergone such a technique is referred to as a copy-controlled CD (CCCD).
In order to prevent copying action, erroneous data or inaccurate data (hereinafter called false TOC data) are generally recorded on a TOC (Table of Contents) where track information or the like is recorded. For instance, false data representing that a time—at which read-out operation is commenced—starts from zero have been recorded in the TOC in advance. An ordinary CD player can properly reproduce audio data by neglecting the false data. The optical disk drive built in the PC first reads the TOC data and hence “believes” the false data included in the TOC data, thereby immediately shifting from read-in operation to read-output operation. Thus, audio data cannot be read. Alternatively, AUDIO data showing audio data should originally be recorded in the TOC data. However, false “DATA” data showing digital audio are recorded in the TOC data to cause a controller of the optical disk apparatus to erroneously determine the audio data as digital data, thereby causing a read error.
There has also been proposed a method for dividing the CD into two sessions; i.e., a first session and a second session; recording normal data in a TOC of the first session and audio data; recording false data in a TOC of the second session; and recording, in the form of digital data, software and compressed files, which are specifically designed for causing the optical disk drive built in the PC to reproduce data.
FIG. 5 shows the configuration of such a multi-session CD. A CD 10 is divided into a first session and a second session. Each session has a read-in area, a data area, and a read-out area. Data are usually recorded in the read-in area, the data area, and the read-out area in accordance with a red book standard, or a yellow book standard for expanding the red book standard. Data are divided on a per-frame basis, an done frame includes synchronization data SYNC, a sub-channel, data, and a parity. One sector is constituted of an aggregation of 98 frames, and a sub-channel block is constituted of sub-channel data included in the 98 frames in one sector. The sub-channel block includes Q data and the synchronization data SYNC showing the start of the sub-channel block. The Q data include a track number, a track start time, and the like. The Q data in the read-in area differ in format from the Q data in the data area and the read-out area, and the Q data in the read-in area impart the so-called TOC. The drawing shows the read-in area 11 in the first session and the read-in area 13 of the second session, and the TOCs of the respective sessions are recorded in these read-in areas 11, 13.
FIG. 6 shows an example of the TOC data of the first session. The TOC data include a track number TrK 14, a data format 22, a start time (minutes Min and seconds Sec) of each track, a frame number Form 16, a logic block address LBA 18 computed from the absolute time, as well as a read-out start time and a logic block address 20.
The TOC data of the second session include false data. For instance, information items ranging from the first to fifth tracks are recorded in the TOC of the first session. Information items ranging from the second session to the sixth session should originally be recorded in the TOC of the second session. However, false data formats and start times of the first to fifth tracks of the first session are also recorded.
When data on such a CCCD are reproduced by an ordinary CD player, audio data pertaining to the first session are reproduced, thereby reproducing ordinary sound. When the data on the CCCD are reproduced by the optical disk drive built in the PC, reproducing operation is performed by reading the custom-designed software and compressed files, which correspond to digital data recorded in the second session.
When an attempt is made to copy the CCCD with the optical disk drive built in the PC, processing is performed on the basis of the false TOC data in the second session, thereby failing to read the audio data in the first session. Thus, retry is performed frequently, and consequently copying of the CCCD is prevented (the optical disk drive goes to read audio data as digital data while “believing” the false data format, thereby failing to find an appropriate header or synchronization data SYNC of the sector).
In relation to the CCCD, there is also practiced recording of data by intentionally offsetting synchronization data SYNC included in the sub-channel. In this case, the timing at which data are to be read is offset, and hence reproduction of data from the copied CD results in generation of sounds having a high level of noise. Japanese Patent No.3405980 describes a CCCD.
Even when a user desires to duplicate a CD for only private purposes and retain the resultant copy for backup, the CCCD cannot be copied, whereby the user's convenience is deteriorated.